Conventional internal combustion engines are inefficient in the combustion of their fuel. Compression ignition engines that use diesel fuel are particularly inefficient because of the relatively slow burning nature of the diesel fuel so that exhaust with incomplete burnt fuel is discharged. This problem is exacerbated when the vehicle is under load and more fuel is provided to the engine.
To address this problem, a dual fuel engine system was developed where LPG fuel was introduced to the engine to improve the efficiency of the combustion of the diesel fuel. Current dual fuel engines often operate on diesel only for part of the operating range of the engine and on the combined use of the diesel and LPG fuel for the rest of the operating range. In many situations LPG fuel flow rate is subject to limited or no control. In some dual fuel engines the LPG flow rate is controlled by the air intake rate to the engine. In contrast, other engines control the supply of LPG through the governor for the diesel fuel. These mechanisms in controlling the supply of LPG to a dual fuel engine system do not appear to adequately address safety issues, accessibility to the LPG supply controls nor optimize the efficiency of engine performance and fuel combustion.